In the related art, light scanning microscopes of the type having a stick-type objective lens that enables the observation of a deep point inside a specimen, such as a living animal, when being stuck in the specimen (e.g., see Patent Literature 1) are known. A light scanning microscope described in Patent Literature 1 includes a focus adjusting unit disposed between a stick objective lens and an image forming lens that forms an image with light collected by the stick objective lens. Furthermore, it is possible to change the focal point without moving the stick objective lens itself by relatively moving two lens groups constituting the focus adjusting unit in the optical-axis direction, while changing the magnification of projection from the scanning unit to the stick objective lens to correct the observation range that would otherwise change with the movement of the lens groups in the focus adjustment unit.